1. Field of the Invention
The present invention relates to a radiation detector used for medical diagnosis, nondestructive inspection, and the like, and a scintillator panel used for the radiation detector.
2. Description of the Related Art
Conventionally, a radiation image such as an X-ray image is widely used for diagnosis of disease in medical fields. In recent years, digital system radiation detectors appear, which are represented by a flat panel type radiation detector (Flat Panel Detector: FPD) that can directly obtain a digital radiation image.
Such a digital system can obtain a digital radiation image and can display the image on an image display device such as a cathode ray tube and a liquid crystal panel, so that it is not necessarily required to form the image on a photographic film. As a result, these digital system radiation detectors reduces the necessity of image forming by silver halide photography and significantly improve convenience of diagnostic work in hospitals and clinics.
Some flat panel type radiation detectors (FPDs) employ a scintillator system which converts radiation into light by a scintillator such as Gd2O2S and CsI and thereafter converts the light into electric charges by a photodiode. Such a scintillator system FPD is formed by combining a scintillator panel in which a phosphor layer is formed on a substrate and a photoelectric conversion element member including a thin film transistor and a charge-coupled device.
In the scintillator panel used in such an FPD, when the phosphor layer formed on the substrate has moisture absorbency, a moisture-proof protective body is provided to cover the substrate and the phosphor layer so that moisture is prevented from reaching the phosphor layer and deteriorating the phosphor layer.
For example, as shown in FIG. 5, JP 2006-38870 A discloses a scintillator panel 100 in which a phosphor layer 104 is formed on a resin substrate 102, and thereafter a first moisture-proof protective body 106 is provided so as to cover from a surface of the phosphor layer 104 to a part of a surface of the resin substrate 102 opposite to a surface on which the phosphor layer 104 is formed, and further a second moisture-proof protective body 110 is formed on a portion of the resin substrate 102 other than a portion of the resin substrate 102 on which the first moisture-proof protective body 106 is provided and on the first moisture-proof protective body 106 on the resin substrate 102 through an adhesive layer 108.
As shown in FIG. 6, JP 2011-33563 A discloses a scintillator panel 200 in which a phosphor layer 204 is formed on a metallic hard substrate 202, and thereafter a moisture-proof protective body 206 is provided so as to cover from a surface of the phosphor layer 204 to a surface of the hard substrate 202 opposite to a surface on which the phosphor layer 204 is formed.
The moisture-proof protective body 206 of the scintillator panel 200 is formed by placing the hard substrate 202 on a rotating table in a supportive manner through a plurality of supporting needles and, in this state, performing vapor deposition while rotating the rotating table in a vapor deposition apparatus using a CVD method.
By forming the scintillator panels 100 and 200 in this manner, it is possible to prevent moisture from reaching the phosphor layers 104 and 204 and to continue a desired function without deteriorating the phosphor layers 104 and 204.
However, in the scintillator panel 100 disclosed in JP 2006-38870 A, as shown in FIG. 7, although moisture is prevented by the first moisture-proof protective body 106 and the second moisture-proof protective body 110, moisture may reach the phosphor layer 104 from the adhesive layer 108 between the resin substrate 102 and the second moisture-proof protective body 110 through the resin substrate 102 as indicated by arrows, so that it is not possible to perfectly prevent moisture from reaching the phosphor layer 104.
Further, in the scintillator panel 200 disclosed in JP 2011-33563 A, although it is possible to perfectly prevent moisture from reaching the phosphor layer 204 because the moisture-proof protective body 206 covers the hard substrate 202 and the phosphor layer 204, as shown in FIG. 8, when forming a radiation detector 220 by bonding together the scintillator panel 200 and a photoelectric conversion element member 210, there is a case in which air 230 remains between the scintillator panel 200 and the photoelectric conversion element member 210 and air gaps occur between them when bonding together the scintillator panel 200 and the photoelectric conversion element member 210 because the hard substrate 202 is used in the scintillator panel 200.
In the scintillator panel 200 of JP 2011-33563 A, if the hard substrate 202 is replaced by a soft resin substrate, when bonding together the soft resin substrate and the photoelectric conversion element member 210, it is possible to bond the photoelectric conversion element member 210 to the scintillator panel 200 by following small unevenness on the scintillator panel 200. Therefore, it is considered that it is possible to prevent the air 230 from remaining between the photoelectric conversion element member 210 and the scintillator panel 200.
However, in this case, a soft resin substrate is used, so that when forming the moisture-proof protective body 206 in a vapor deposition apparatus using a CVD method, it is difficult to maintain the resin substrate horizontally straightforward, and the moisture-proof protective body 206 is formed in a state in which the resin substrate is deflected.
When bonding together the scintillator panel 200 obtained in this manner and the photoelectric conversion element member 210, the scintillator panel 200 is restored from the deflected state to the straightforward state by the photoelectric conversion element member 210. Therefore, in some cases, the moisture-proof protective body 206 is broken and the moisture-proof property of the phosphor layer 204 degrades.